A study conducted by a research team at Albert Einstein College of Medicine of Yeshiva University suggests low levels of Vitamin D may increase an individual's risk for peripheral artery disease (PAD). Their findings, presented at American Heart Association's Arteriosclerosis, Thrombosis and Vascular Biology Annual Conference 2008, were derived from an analysis of blood samples collected from 4,839 adults.

PAD is a common disease present in 10-25% of people over the age of 55, and results when fatty deposits clog arteries leading to the legs, narrowing the path for blood to pass through. Patients with PAD report pain or numbness in their legs, and often an inability to walk. According to the American Heart Association, individuals with PAD are at a higher risk for both heart attack and stroke.

Vitamin D can be made in the skin upon exposure to sunlight or obtained from fish and dairy products. Vitamin D's role in bone health is well-established, yet only recently have scientists begun to investigate its effect on cardiovascular health.

The research team decided to pursue the experiment after considering the vascular physiology of mice. "We know that in mice, vitamin D regulates one of the hormone systems that affects blood pressure," said Dr. Michal Melamed, the group's lead investigator and assistant professor of Medicine at Einstein. "Since cells in the blood vessels have receptors for vitamin D, it may directly affect the vessels.."

Using the ankle-brachial index, Melamed's team analyzed a survey of 4,839 adults. The ankle-brachial index is a measure of the fall in blood pressure in the legs, and is a typical screening tool used to diagnose PAD. An individual's score is determined by dividing systolic pressure recorded at the arteries in the ankle by the systolic pressure of the arteries in the arm. A ratio between 1.3 and 0.9 is considered normal, whereas scores below 0.9 indicate disease, and a score below 0.5 indicates severe disease. Melamed's lab also analyzed other risk factors for PAD, including elevated cholesterol levels, high blood pressure, and presence of diabetes.

Their study found a correlation between low levels of vitamin D and prevalence of PAD. Among the group with the lowest levels of vitamin D (less than 17.8 ng/mL), 8.1% had PAD. In the group with the highest levels of vitamin D (29.2 ng/mL), only 3.7% had PAD. Adjusting the study for sex, age, and co-existing health problems, Melamed's team concluded PAD was 64% more common in the group with lower levels of vitamin D than in the group with higher levels. Furthermore, for each 10 ng/mL drop in vitamin D, the individual's risk for PAD increased by 29%.

Dr. Melamed recognizes that this is still just a correlative study, and while the findings do suggest a role for vitamin D in PAD, it is possible that vitamin D is merely a marker for other variables such as a healthy diet. Proving causation would require a randomized study, administering vitamin D to one set of patients while holding one set constant,something that hasn't been done yet.